Typically, a lubrication system is provided in most rotating machinery such as engines, turbines, pumps and the like. The non-conducting fluid such as lubricating oil is supplied to various wear points which are protected by bearings or other friction-reducing devices.
Prior to a total bearing failure and seizure of the rotating apparatus, small metal particles are emitted into the lubricating oil. Depending on the size of the rotating equipment, many variables of the lubrication system, (i.e. the metals of various bearing assemblies and other factors) determine how serious this problem is. The metal particles may be quite small or substantially large, and may vary in number from an occasional particle to a great number of particles, all of which can be indicative of failure conditions. In view of the great variety of circumstances, it will be understood and appreciated that a need has arisen for a metal bearing failure detector which is sensitive and responsive to particles of a given size or quantity, and which is not triggered by or responsive to a lesser number of particles in such circumstances.
U.S. Pat. No. 3,422,417 to Lowe, which is incorporated herein by reference, shows such a basic device which has been in use for many years. A problem with this prior art device is that if the insulation becomes hot and either melts out or is burned out because of a fire, or does not adhere properly, lubricating oil will leak into the electrical wiring cavity and the alarm system will fail. This problem is exacerbated because such failure can go undetected since it essentially disarms the alarm system without notification to the user. Consequently, the device being protected by the alarm system can essentially go undetected if the alarm system fails, and this of course can cause the primary equipment being protected, such as an engine, turbine, etc., to fail, at great expense to the user.
Consequently, there is a need for an improvement to the prior art metal particle detector devices such as that shown in the aforementioned Lowe patent to overcome the melting or burning insulation or adherence problem and to provide for early detection when the detector/alarm system is about to malfunction for this reason. If adhesion of the elastomeric seal is poor in the Lowe arrangement due to poor manufacturing processes, vibration during operation or high pressures may cause the seal to leak.
Additionally, there is considerable expense involved in the manufacture and insulation of the Lowe metal particle detector system because the metal plate detector unit must be insulated around the edges thereof. Accordingly, there is a need for a simpler and more dependable way of installing and using one of these detector units.